Microstructural and electrical properties of multicomponent varistor ceramics with PbO-ZnO-B2O3 glass addition

Zinc oxide based ceramics are widely used materials in varistors because of their excellent nonlinearity. Traditionally these ceramics are sintered at high temperatures (about 1,100-1,300 degrees C). In this work a novel zinc oxide-based material with a low sintering temperature (900-1,000 degrees C) was investigated. This material can be used in varistors consisting of several ceramic layers with embedded silver/palladium thick-film electrodes. This paper explains the research procedure employed with this novel varistor material, including the effect of sintering aid addition on the final electrical properties and fired microstructure. The electrical properties achieved are compared to the values measured from the original zinc oxide composition without sintering aid addition. Especially the I-V characteristics, nonlinearity coefficient alpha, breakdown voltage V-bk and leakage current density J (L) are investigated. The sintering properties are also reported. It was found that by adding 10 wt.% of glass and using a 900 degrees C sintering temperature, the material had good varistor characteristics, as VbkCe=Ce378 V/mm, alpha Ce=Ce33 and J(L) Ce=Ce15 mu A/cm(2). The investigated varistor material can be applied to protect electrical circuits against surges.